What is another word for fast-acting?
Pronunciation: [fˈastˈaktɪŋ] (IPA) 
When it comes to describing something that works quickly, the term "fast-acting" is often used. However, there are many other synonyms that can be employed to convey the same idea. One such option is "rapid," which implies a high level of speed and efficiency. Alternatively, "swift" can be used to describe something that acts quickly and decisively. "Expeditious" is another option, carrying connotations of efficiency and promptness. "Prompt" and "immediate" also convey a sense of urgency and rapidity. Ultimately, the synonym chosen depends on the context and desired tone, but these options all effectively convey the notion of something happening quickly.
